Regulation of the voltage of alternating-current machines.



C. A, PARSONS & A. H. LAW.

REGULATION OF THE VOLTAGE OP ALTERNATING CURRENT MACHINES.

APPLICATION FILED SEPT. 16, 1910.

1,005,293. I Patented Oct. 10, 1911.

2 SHEETS-SHEET l.

C. A. PARSONS & A. H. LAW. REGULATION or THE VOLTAGE or ALTERNATING CURRENT MACHINES.

APPLICATION FILED SEPT. 16, 1910,

Patented Oct. 10, 1911.

Jew,

UNITED STATES PATENT OFFICE. I

CHARLES ALGERNON PARSONS AND ALEXANDER HENRY LAW, OF NEWCASTLE-.UPON- TYNE, ENGLAND; SAID LAW ASSIGNOR TO SAID PARSONS.

REGULATION OF THE VOLTAGE F ALTERNATING-CURRENT MACHINES.

Specification of Letters Patent.

Application filed September 16, 1910.- Serial No. 582,864.

Patented Oct. 10, 1911.

To all wlwm it may concern: Be it known that we, CHARLES ALGERNO PARSONS and ALEXANDER HENRY LAW subjects of the King of Great Britain and Ireland, residing at Newcastle-upon-Tyne, in the county of Northumberland, England, have invented certain new and useful Improvements in and Relating to the Regulation of the Voltage of Alternating-Current Machines, of which the fication.

This invention relates to the regulation of the voltage of alternators for the purpose of keeping the voltage constant and particularly to apparatus for this purpose such as that described in Letters Patent 925499 in which the voltage is regulated by varying the current passing around a leakage path of magnetic material laced across the poles of the alternator or o the exciting machine. In such devices it is -usual to arrange the amount of the compounding action of the device so as to kee the voltage nearly con,- stant when the mac ine is working on a load having a low power factor. In such cases owing to the fact that an alternator requires a much greater exciting current when working with a lagging current of low power factor than it does when working with a cur following is a speci rent having a power faptor of unity the alternator will be considerably over-compounded when working with a power factor of unity if desired so that the voltage is practically, constant as the load increases with a power factor of say 80 per cent. In some cases it is convenient, where such leakage paths a're used, to supply the current to the leakage path by means of static current transformers, arranged to give a secondary current proportional to the main current.

The object of the present'invention is to provide means whereby compounding devices such as that above referred to and described in the Letters Patent No. 925499 in the names of (1A. Parsons and A. H. Law,

may be made to automatically supply the right amount of compounding for loads having different power factors. The 1nvent1on conslsts 1n causing the cur-.

matically varyin the reluctance of the magnetlc circuit of t e static transformer which supplies current to the winding of the leakage path in such a manner that the current in said winding is greater when the load is inductive than when it is non-inductive.

The invention further consists in providing an inductor rotating in synchronism with the alternator and in inductive relation with the magnetic circuit of the transformer which supplies current to the winding of the leakage path, the inductor being so arranged that the current in the secondary of the transformer and consequently in the winding of the leakage path is greater when the current lags behind the voltage causing the power factor to be less than when the current-is in phase with the voltage.

The invention further consists in the means for causing the current in the leakage path to be greater when the load is inductive than when it is nominductive hereinafter described.

Referring to the accompanying diagrammatic drawmgs: Figure 1 shows an arrangement in which the regulating device is applied to regulate the voltage of an alternator. Figs. 2 and 3 show the transformer of Fig. 1, with the rotating inductor in dif ferent positions. Figs. 4, 5 and 6 show an arrangement for three phase working. Fig. '7 shows a form in which the inductor carries the primary winding of the transformer. Figs. 8, 9 and 10 show a form of the device in which the inductor carries part of the primary winding, while Figs. 11 and 12 show other forms of the device.

- In carrying the invention into effect, a winding on the leakage paths or other compounding arrangements of the alternator whose voltage is to be regulated is supplied with an alternating current of magnitude proportional to the load on the alternator by means of a suitable transformer such as that shown in Figs. 1, 2 and 3.

The primary winding, cl, and secondary winding, e, are wound ona magnetic circuit, a, a, including an inductor, b, which is usuall formed of laminations and revolves in a circular bore in the iron path, a, which bore is similar to that between the magnet poles of a dynamo. The inductor, b, is shaped so that when rotating it interrupts the magnetic circuit of the transformer by interpos'ing a large air gap in some positions,

while in others it com letes the magnetic circuit. In order to uti ize this variable reluctance for the purposes of the present invention, the inductor is keyed on theshaft, c, in such a position that at the time of maximum current in the primary winding, the air gap in the magnetic circuit is a maximum or nearly so for a power factor of unity, consequently the magnetic reluctance of the complete iron circuit is large and the current in the secondary winding, 6, small. \Vhen however the primary current lags behind the voltage on account of a low power factor, the inductor, b, is arranged to produce a small magnetic reluctance at the time of maximum current in the primary winding, d, and consequently the secondary. current will then be great.

In Fig. 1 the inductor is shown in the position when the current in the primary winding, d, for a load factor of unity, is a maximum, while in Figs.'2 and 3 the positions of the inductor correspond substantially to power factors of 80% and respectively, the current in the primary winding being at its maximum for the position shown. When such a device is used for thepurpose of regulating the voltage of an alternator, it is connected with the latter in the manner shown .in Fig. 1, the primary, d, of the transformer being in the main external circuit of the alternator, while the secondary winding, 6, supplies current to a winding, is, on a leakage path, n, between adjacent poles, 0, of. the alternator.

Forthe'sake of simplicity, only one leaka'ge path, n, has been shown, though it will be understood that it ispreferable to have one path connecting each pair of poles of opposite polarity, that is there will be three such paths for the six pole alternator shown,

alternator is a lagging one, and thus acting to de-magnetize the magnetic field of the alternator and produce a decrease in the terminal voltage, the inductor b, will be adjusted to be in-a position in which the magnetic reluctance of the transformer is least, the current in the primary winding being then a maximum. The leakage path winding, is, is thus supplied with ,a greater current which decreases the amount of leakage of the main magnetic field of the alternator, and prevents any decrease in the termlnal voltage. In a similar manner, overcompounding of the alternator is prevented in cases in which the current is in phase with or leads the voltage. In the first of these cases clearly the voltage induced in the secondary winding of the current transformer will be lower than in the second case and consequently if the inductor is suitably keyed on the shaft the current in the \coils around the leakage paths of the main alternator will be less when the current is in phase with the voltage than when it is lagging behind the voltage. In' this arrangement the reduction in current in the secondary windings is effected in two ways, firstly, the reluctance of the magnetic circuit being increased while the current in the primary winding is a maximum fewer lines of force thread the magnetic circuit,. secondly, if the secondary winding is suitably placed, the leakage co-eflicient is greatly increased by interposing an increased air gap and consequently of all the lines of force induced'by the primary windings only a comparatively small number pass through the secondary winding. If desired, various devices may be used to increase this action, for instance, as indicated by the dotted lines in Fig. 3 iron shunting paths y may be inserted, which when the magnetic circuit is interrupted. will allow a considerable number of lines of force to leak back without, acting on the secondary windings. When however, the magnetic circuit is nearly complete, the effect of these alternative paths will be comparatively small. Further these shunting paths may bemade to rotate synchronously in such a way as to cause greater leakage when the power factor is unity than when the current is lagging behind the voltage and the power factor is consequently low.

The inductors maybe driven either directly by the alternator or through gearing or by a synchronous motor.

Figs. 4, 5 and 6 show an arrangement for three phase working, one suitably shaped inductor f being used to interrupt the magnetic circuit of a three phase transformer. In each figure g is the transformer core having three limbs, h, i, and 7', each limb carrying the primary windings Z and secondary windings m in connection with one phase ofv a three phase alternator. The inductor is assumed keyed in the same position on its shaft, 6, and is shown in the positions relatively to the upper limb, j, at the moment of maximum current for power factors respectively of 100%, see Fig. 4, see Fig. 5 and 50% see Fig. 6.

According th another modification of this invention shown at Fig. 7 the iron circuit a, a of the transformer contains an inductor b which carries a winding p. This inductor is rotated at a speed synchronous with the speed of the alternator, and in one form the windings on the inductor carry the primary current of the transformer.

On the 1mm circuit of the transformer a secondary winding 6 is placed in whlch 1s generated thecurrent which is supplied to the leakage path. The

inductor is so keyed on its shaft that when the power factor of the alternator circuit is unity, its magnetizing effect on the iron circuit of the transformer is small at the moment when the primary current is a maximum. When, however, the current in the primary maximum lags behind the voltage of the alternator, the inductor is in such a position when the primary current is at its maximum that the magnetizingeifect on the iron circuit of the transformer is greater and consequently in this case the secondary current supplied to the leakage path will be greater. In this modification of the invention the whole of the winding may be carried on the inductor and the secondary winding be arranged on the core of the transformer, or as shown in Figs. 8, 9 and'10 only part of the primary winding 03, d may be put on the inductor, the remainder being arranged on the transformer core.

In Figs. 8, 9 and 10 the inductor g is assumed to be keyed in the same position on its shaft and is shown in the position relatively to the transformer iron circuit at the moment of maximum current for power factors respectively of 100% see ig. 8, 80% see Fig. 9, and 50% see Fig. 10. In this arrangement the part'of the primary windiig (Z on the inductor is assisting the part of the primary winding d on the transformer core,

and it will be seen that with a lagging current the magnetizing efiect on the transformer core will be greater than with a power factor of unity, and consequently, the currents induced in the secondary windings, e, which are supplied to the leakage path will be greater. Also, alternatively, thesecondary winding may be arranged Wholly on the inductor, or partly on the inductor and partly on the transformer core, the primary winding being on the transformer core, or both primary and secondary may be wholly or partly on the inductor and transformer core.

In cases where the primary winding is wound both on the inductor and on the transformer core, as shown in Figs. 7, 8 and 9, the part on the core may be wound in the same or opposite direction and thus willeither assist'or oppose the remainder of the winding, and the two parts may be coupled in series or be separately supplied with primary current.

According to a further modification the synchronously revolving inductor or Wound rotor instead of being used in a current transformer adapted to supply a leakage path or other compounding device, may be applied directly to the leakage path or paths.

,nations as to choke back the leakage Considering for'a moment the simple case of a single leakage path bridging" the poles of a magnet. It 1s clear that a wound rotor, interrupting the leakage path and carrying} in its windings either the inain current of the alternator or a current proportional to same obtained from a current transformer can be so set in relation to the currentalterthe leakage flux in the current instead of the choking action belng llmlted to every alternate alternation as 1n the case of an ordinary leakage path with a stationary winding. Further the relation of the position of the round rotor on the shaft to t e current alternations can be so dlsposed that its action is much stronger when the current is lagging behind the volt age than when the two are in phase. Flg. 11 shows a synchronously revolving inductor 1' interrupting a leakage path, s of one of the types described in Letters Iatent No. 925 199. This inductor 1', carries a winding w whichwhen excited will have the effect of reducing the leakage with'every alternation of the main current since with every alternation it reverses-its position. In place of applying the above wound rotor for the purpose of reducing the leakage in the leakage paths it is clear that it can equally be used to increase the fiux in the magnets with every alternation as shown in Fig, 12 and can be arranged also.to have a stronger action when the power factor is low than when it is-high'. Also it can con- 100 veniently be applied to polyphase'instead of single-phase currents as'described. Further an unwound rotor canbe applied to theleakage paths to increase their action with a poor power factor. In this case it would be 1 so set on the shaft in relation to the altemations that with a poor power factor the inductor would keep down the leakage fiux in the leakage paths at the moment when little or no current is passing in the leakage path 1 windings; when however the leakage flux is eifectually blocked by the current-in the windings it would be in such a position as to close the magnetic circuit of the leakage paths, but the current in the windings would 1 then stop the leakage. IVith a-high power factor this action would be reduced and consequently the action of the leakage path would be less.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is I 1. In alternators, means for regulating the voltage according as the load is inductive or non-inductive,comprising a magnetic circuit and an inductor rotating synchronously with the frequency of the alternator current, and adapted to vary the reluctance of said circuit.

2. In alternators, means for regulating the voltage comprising a leakage path, a wind- 139 path with every alternation of 75 I ing on said leakagepath, means for supplying alternating current to said winding and an inductor rotating synchronously with the frequency of the alternator current, and adapted to vary the strength of the current in said winding.

3. In alternators, means for regulating the voltage comprising a leakage path, a winding on said leakage path, means for supply-- ing alternating current to said winding, said means including a transformer and an inductor rotating in the magnetic circuit of said transformer at a speed depending upon that of the alternator.

4. In alternators, means for regulating the voltage, comprising in combination an exciter for the field magnets of the alternator, a leakage path between the poles of said exciter, a winding on said leakage path, a transformer whose primary circuit is supplied with alternating current proportional to the load, and whose secondary circuit supplies current to said winding on the leakage path and an inductor rotatlng in the mag netic circuit of said transformer at a speed depending upon that of the alternator.

5. In multi-polar alternators, a device for regulating the voltage under a varying load and power factor, comprising a leakage path between adjacent poles of the alternator, a winding on said path and means for regulating the magnitude of an alternating current passing through said winding according-to the power factor or the loadon the alternator.

'6. In combination with an alternator having a plurality of poles, a transformer having primary and secondary windings, the former being in the main circuit of the alternator, a leakage path between adjacent poles of the alternator and a winding on said path connected to the secondary winding of the transformer and a variable magnetic reluctance in the transformer magnetic circuit, the magnitude of said reluctance being adjusted to maintain the voltage of the alternator uniform for all values of the load power factor.

7. In combination with an alternator hav ing a plurality of poles, a transformer having primary and secondary windings, the former being in the main circuit of the alternator, a: leakage path between the adjacent alternator poles and a winding on said path, said winding being in the secondary circuit of the transformer, an inductor rotating synchronously with the alternatorto vary the air gap in'the transformer magnetic circuit whereby on varying said gap the secondary current of the transformer is regulated in accordance with the power factor of the alternator load to prevent any variation I in the alternator voltage.

8. In combination with an alternator having a plurality of poles, a leakage path between adjacent poles, a winding on said path, a transformer having its primary connected to the main circuit ofthe alternator and its secondary in circuit with the leakage path winding, an inductor rotating at a speedsynchronous with the frequency of the alternator current and-adapted to vary at every revolution an air gap in the transformer magnetic-circuit, whereby on adjusting the phase relationship of the maximum air gap to the maximum primary current in the transformer, the current in the leakage ath winding is regulated to maintain the voltage of the alternator constant for all values of the power factor.

9. In combination with-an alternator having a plurality of poles, a leakage path between adjacent poles, a winding on said path, a transformer having its primary connected to the main circuit of the alternator and its secondary in circuit with the leakage path winding, circular cross section rotating in the transformer magnetic circuit at a speed synchronous with the frequency of the alternator current, whereby on adjusting the phase re lationship of the maximum air gap to the maximum primary current in the trans former, the current in the leakage path winding is regulated to maintain the voltage of the alternator constant for all values of the power factor.

In testimony whereof, we afiix our signatures in presence of two witnesses,

CHARLES ALGERN ON PARSONS. ALEXANDER HENRY LAW.

Witnesses:

FREDERICK GORDON HAY BEDFORD, ALBERT WILLIAM PARK.

a laminated inductor of non- 

